An LED (Light Emitting Diode) used for illuminations, a backlight of a display device, or the like is controlled by a driver circuit device. A driver circuit device receives inputs of a control signal for controlling turning on/off and brightness of an LED and a clock signal for determining a control timing for the LED and controls the LED in synchronization with the clock signal and in accordance with the control signal.
However, a conventional driver circuit device requires two signal lines (harnesses) to transmit the control signal and the clock signal. When the two harnesses extend over a plurality of printed circuit boards, there is a problem that the number of the harnesses becomes large or the entire length of the harnesses becomes long.